The Stovebolt Site Forums The Shop Area Driveline Drilling steering arms

I'm installing a disc brake kit and the bottom bolts that go through the spindles and into the steering arms have to be drilled from 7/16" out to 1/2". I bought some cobalt bits and was able to drill the spindle holes pretty easily. The steering arms are a whole other story. I've destroyed four expensive bits trying to drill these things. Come to think of it, I'm constantly destroying drill bits. Is there some trick to drilling steel without going through $100 worth of drill bits? Or is that just the way it is? I try to go slow, use some oil.... but no luck.

If the chips are blue, slow down the bit, use lubricant.

Ed

Enlarging holes is hard on twist drills, as the force is concentrated on the tip of the bit. If you're using a hand drill motor, you're probably binding and breaking the bit cutting edge because it's hard to keep them aligned. To successfully drill these, you probably need to clamp them in a drill press, center the existing hole, and has been said go REAL slow with plenty of lubricant.
Another option is an adjustable reamer, taking just a tiny bit off each pass, and adjusting the reamer until you get to the desired size.

Use a drill press, slow the cut down, and step-drill the hole bigger about 1/32" at a time. Use a good quality lubricant like Rapid Tap or Tap Magic, or plain old 30 weight motor oil if nothing else is available. A can of STP and a pound of unsalted lard makes some of the best general purpose cutting oil available. Mix the STP with the lard until you get a stiff liquid a little thicker than honey that clings to the drill bit when it's applied with a small paint brush. Mix half a cup or so at a time, and your supplies will last a few years. When the chips get hot on a heavy cut, that mix smells like bacon frying.
Jerry

Yes, you guys hit the nail on the head. Its getting very hot and binding like crazy. I'm using the lightest pressure but still grabbing. Ha! unsalted lard?? I'll have to ask the wife about that one. I'm not from the south.... Thanks for the advice guys, I'll give it a shot.

Your local "Habla Espanol" restaurant uses it by 50-lb. cans in most of the food they serve, particularly refritos! If you ask nicely, they'll probably give you some!
Jerry

Or any Hispanic grocer. They've started carrying it in little tubs (like softened butter) in fact. But don't look in the refrigerated section. It will usually be in the aisle with baking supplies...next to Crisco, shortening, etc.